Rotary underreamer and cutter element therefor



Feb 9, 1932 J. GRANT I E 1,844,357

ROTARY UNDERREAMER AND CUTTER ELEMENT THEREFOR Filed Jan. 22, 1930 QYV I I /P Patented Feb. 9, 1932 UNITED STATES JOHN GRANT, OF. LOS ANGELES, CALIFORNIA ROTARY UNDERBEMER AND CUTTER ELEMENT THEREFOR Application filed January 22, 1930. Serial No. 422,583.

This invention has relation to rotary reamers and has to do more particularly with improvements in cutter mountings for such reamers to enable the parts better to withstand the large pressures and stresses to which they are subjected.

The improvements in cutter mountings set out herein are generally applicable to any type of reamer wherein a cutter element or cutter carrier is mounted in a body slot and bears laterally against a side wall of the slot for support against im osed stresses. The invention, as will be reac ily understood from what follows, is not necessarily limited to any particular type of reamer or underreanier; but, because the practical use of the present improvement is to be found most largely in underreamers, I explain the invention in connection with a particular type of underreamer. Again it will be understood that the invention is not limited to its applicability to the details of that particular type. For instance it will be easily understood from the following description that the invention has applicability wherever the cutter element or cutter carrier is mounted in a body slot, or is so mounted in or on a body that it bears laterally against a body wall. Thus it is immaterial whether the cutter carrier moves in,

w or is stationary with relation to, the body slot.

Bearing these things in mind I shall proceed to a description of the invention specifically as applied to the type of underreamer which is set out in the Phipps Patent No. 1,67 8,07 3, dated July 2%, 1928, and also set out in my application Serial No. 25 L266, filed February 1st, 1928. In that type of reamer there is a tubular body having longitudinally extending slots through a tubular wall. An internal mandrel is utilized to cause expansion and contraction of the cutters as they move vertically on the mandrel; and the cutter carriers are mounted in the body slots to be vertically movable therein and to pro termed the back side of the carrier, a bearing ject outwardly through the body expanded.

In that type of reamer, as in any reamer wherein cutter carriers are mounted in body slots or the equivalent, the cutters are sub jected to very large pressures which are not directly radial of the tool but which have a heavy circumferential component. That component stress is at times so heavy, and presses the cutter carrier against the side wall of the slot with such great force, as to deform either the cutter carrier or the bearing face of theslot wall, or both. v i i It is a common practice to use roller cutters as the ultimate cutting elements of such tools; and the cutter carriers have been formed with a head or hearing block at the upper end, and another head orbearing block at the lower end, and with a recess between the two heads for receiving the roller cutter. In that particular design it has usually been the case that the upper and lower heads of the cutter carrier have been substantially the only parts of the carrier which project out through the body slot and which therefore afford a bearing for the carrier upon the slot wall. The effective bearing faces being thus of limited extent, large imposed forces have caused excessive wear and at times have actually deformed the bearing surface of the slot wall by forcing the heads of the cutter carrier into that slot wall.

The present invention overcomes these difficulties by providing, on what will be slots when web which makes the bearing of the carrier on the slot wall substantially commensurate with the length of the carrier itself. The particulars and details of how this is done will be now described as a typical and illustrative embodiment of, but not of necessary limitation upon, the invention. For this purpose reference is had to the accompanying drawings in which I Figure 1 is a longitudinal section showing has a tubular body 10 with wall slots ll,..said.

slots extending through the wall and being elongated vertically, orlongitudinally of the body axis. Withinthe bodyis located an internal mandrel 12 which acts as a cutter expanding mandrel anclzas a cutter support ing abutment. The cutter carriers 13 he in the body slots and have inn/er faces contacting with the mandrel; and the mandrel :is so shaped @(in this ease having an upper relatively large part 12a) that. upward movement of the cutter carr iers from the position of Figure lto the position xof :Figurezfl causes out ward expansive movement of the carriers.

' -Ehis upward'movementiscaused a spring 155 which pushes :upwardly 1 on .:a cutter y pro- "peller 16; All rthisavil libe readily :under- 7 'st'ood from an' inspectien of :thedrawings.

"The cutter carriers as usually used inithis particular type aoff underreamer have embod- V ied a verticwl lyextendingpart 20 with upper and lower "heads 17 and 18, which Lheads' progject outwardily thnough the'ibodyslots nil. Mounted ibetween the aheads is -.the:roliler=cutter '19., rotating on a "vertical axis pin 21 mounted in the heads. lneorder 'to' accommodate @the roller cutter, the portion of the :cutter carrier between the two heads must ibe recessed. A cutter caasriereoffthe general-type 'iherein :described may he looked upon as Ebeing a cutter b'lock or :cutter bar which has -'Ibeen recessed or notched iback from its outer faceato provide a "recess EfOI accommodation :of:therollercutter. And such accessing for the roller cutter has, in past practice, .left substantially billythe :heads M and 18, :or t'heir equivalents, :proj ectin-gi out through the slots, ;or projecting substantially into the slots; and has thus "lleftaon ly the limited @side surfaces=on those heads rto bear. against the .side wall of-the slot. ".Or in fact, such acutiter carrier may considered as comprising 'zt-wo spaced heads between which the roller cutter is mounted. The vertical web '20 in- :terconnects the "spaced headsa'but ithas little :or 'no function of bearing laterally on the slot :wa'll. i

Figure ii) the -usual right handed direcof rotation of the under-recliner is illustrated by the large arrow. During operation, the stresses imposed uponeach -eutter are a radial in-ward pressure indicated'by the arrow B and a more or less tangential pres sure indicated by the arrow T, resulting in a resultant pressure or stress indicated by the arrow S. This resultant stress tends to press the cutter and cutter carrier back against what will be termed the rear wall surface 30 of the slot, and the pressures against that rear wall surface are sometimes exceedinglyheavy, resulting in that excessive wear or deformation which I have noted.

In my improved designI provide, at the rear-side of the -:cutter-.carrier, a weba3l ex tending vertically between the heads 17 and Band -extending outwardly far enough to cover a substantial proportion of the slot wall surface and far enough out to be directlyflbehind the rollercutterlfi), in the direction of thrust'imposed upon it. The spe- -cific,illnstr.ations show the bearing web ofsuch horizontal width as to engage substantialil'yzthe complete rear wall ESLlfIFilmCedOlf the slot. Such (extent may not in allcasesbe necessary itbut it is structurally j ust ras'aeasy to make the- Web .of that ahorizontalwidth, *as to make it =OfJ-lGSSGI"IWld'th,daIld 13116ifillll possible bearing area'x-iseiutilized. Whatever the web widths 1 may the, .the bearing area of the carrier ssupon the slot wall tthus .igneatly increased and the: pressures distributed, so

that the pressure permit :areais much .de Icreased, andzthe SEIITZfEt'CBS cam-take :mdrsupport the heavy stresses without "undue wear ioradeformation. i l

".The :bearing web, such as I :haveadescniibe'd,

V isnecessargy only on "what I term the .rear

side'of the carrier. Gonsequentlyy in order to make room within the'tbody .slotfor :this

7 bearing web, of reasonable rthiclmess, at

thesainetime notzto increase the width :ofthe bodyslot more than is necessary, and "thus to rmaintain unimpaired the strength .of the body; I offset G :of :the roller cutter :from the center 20f the-carrier toward the forward side of the carrier. This-is illusitratedawell in Figure 3 Where the line Glrepresents a radial. :planethrough the center of carrien'andtheo ffsetting'of :the cutter cen- -ter Ciorwardly fIOIIDth lS radial line is apparent. 'Tlietbody slot is, inithis case, cenitered 2.011 the radia'lplane which is parallel with its side walls. However, it will be seen that the-samegeneral :ends may be reached by 'centering'th-e cutter center :on the radial :plane :and slightly unbalancing 1 the slot width as regards thatz-radial plane ;'-in:eith'er lGilSB the roller cutter-center ist-sligli'tly offset forwardly *wit'hlrlation .tothe slot center.

claim: I In; a rotary reamer which comprises a body with. a longitudinally extending wall slot,"

azcutter. carrier in the :body slot and :extendlongitudinally thereof, 'saidcarrier having a head at-each end which heads-project outwardly through the body slot, a roller cutter mounted between the carrier'heads, a

longitudinally extending bearing web extending between the heads at one side only of the roller cutter, the center of the roller cutter being laterally offset from the center of the carrier and of the slot toward the side of the carrier opposite the bearing web whereby to maintain unimpaired the strength of the body so that the reamer can take and support heavy stresses without undue Wear 01' deforlnaticn.

In witness that I claim the foregoing I have hereunto subscribed my name this 14 day of January 1930.

JOHN GRANT. 

